Control of engine intake system

Abstract

A method of controlling an intake air passage of an internal combustion engine is provided. The intake air passage cyclically communicates to a combustion chamber of the internal combustion engine, thereby inducting fresh air into said combustion chamber. The cyclic communication of the intake air passage to the combustion chamber generates a pressure wave in the intake air passage. The method comprises reducing an effective length of a transmission path of the pressure wave in an upstream direction of the intake air passage as a desired air flow to the combustion chamber decreases. In accordance with the method, the effective length of the pressure wave transmission path is reduced as desired air flow decreases. With the reduced effective length, the pressure wave bounces back and forth between ends of the transmission path more often before the next cyclic communication. The more bouncing attenuates the pressure wave at the next cyclic communication. Therefore, the cylinder air charge can be stabilized when the desired air flow is decreased.

1. A method of controlling an intake air passage of an internal combustion engine, said intake air passage cyclically communicating to a combustion chamber of said internal combustion engine, thereby inducting fresh air into said combustion chamber, said cyclic communication of said intake air passage to said combustion chamber generating a pressure wave in said intake air passage, comprising:
 reducing an effective length of a transmission path of said pressure wave in an upstream direction of said intake air passage and retarding beginning of said cyclic communication as a desired air flow to said combustion chamber decreases. 
 
   
   
     2. The method as described in  claim 1 , wherein said beginning of said cyclic communication is retarded after a top dead center of an intake stroke of a cylinder cycle of said combustion chamber. 
   
   
     3. The method as described in  claim 1 , wherein said beginning of said cyclic communication is retarded as desired torque of said internal combustion engine decreases. 
   
   
     4. The method as described in  claim 3 , wherein said beginning of said cyclic communication is retarded as a speed of said internal combustion engine decreases. 
   
   
     5. The method as described in  claim 1 , wherein said effective length is reduced as a speed of said internal combustion engine decreases. 
   
   
     6. The method as described in  claim 5 , wherein said beginning of said cyclic communication is retarded as the speed of said internal combustion engine decreases. 
   
   
     7. The method as described in  claim 1 , wherein said beginning of said cyclic communication is retarded as desired output torque of said internal combustion engine decreases. 
   
   
     8. The method as described in  claim 7 , wherein said effective length is reduced as the desired output torque of said internal combustion engine decreases. 
   
   
     9. The method as described in  claim 1 , wherein said beginning of said cyclic communication is retarded by retarding opening timing of an intake valve of said combustion chamber. 
   
   
     10. The method as described in  claim 9 , wherein a peak lift of said intake valve is reduced as said opening timing is retarded. 
   
   
     11. An engine system comprising:
 an intake air passage; 
 an internal combustion engine having a combustion chamber and an intake valve, said combustion chamber being capable of inducting fresh air from said intake air passage, and said intake valve cyclically communicating said intake passage to said combustion chamber, thereby generating a pressure wave in said intake passage; 
 an air passage adjustor configured to controllably change an effective length of transmission of the pressure wave in said intake air passage; 
 a valve lift adjustor capable of controllably adjusting opening timing of said intake valve; and 
 a controller configured to control said air passage adjustor to reduce said effective length and said valve lift adjustor to retard a beginning of said cyclic communication as a desired air flow to said combustion chamber decreases. 
 
   
   
     12. The engine system as described in  claim 11 , wherein said intake air passage comprises a first air chamber capable of communicating to said combustion chamber with a first effective length of the pressure wave transmission on at least part of said intake air passage and capable of at least partly reflecting the pressure wave, and a second air chamber capable of communicating to said combustion chamber with a second effective length of the pressure wave transmission on at least part of said intake air passage and capable of at least partly reflecting the pressure wave, said second effective length being shorter than said first effective length,
 said air passage adjustor comprises a shutter valve capable of opening and shutting the communication of said second air chamber to said combustion chamber, and 
 said controller is further configured to control said actuator to open said shutter valve as the desired air charge to said combustion chamber decreases. 
 
   
   
     13. The engine system as described in  claim 12 , wherein the fresh air flows through said first air chamber to said combustion chamber.